Contamination with radioactive or chemical substances can have serious consequences for humans and the environment. For this reason, thorough decontamination is of great importance in the decommissioning of nuclear power plants and the remediation of contaminated sites. People who have to carry out such tasks are working under physically demanding conditions and may be exposed to high health risks. To get humans out of those hazardous environments, the ROBDEKON project was launched with the aim of establishing a national competence center for “Robotic Systems for Decontamination in Hazardous Environments”. In ROBDEKON, four research institutions work together with partners from industry to develop practical robot systems for decontamination tasks. The research activities include the development of mobile robots for rough terrain, autonomous construction machines, and robot manipulators as well as decontamination concepts, planning algorithms, multi-sensory 3D mapping of the environment and teleoperation using virtual reality. The focus is on three applications: the decommissioning of nuclear facilities, the decontamination of plant components and handling of waste, and the remediation of landfills and contaminated sites. This paper gives a high-level overview of the goal and the ongoing research activities in ROBDEKON, provides an insight into the infrastructure of the involved laboratories, and presents first project results.